The present invention relates to an improved process for the thermosol dyeing of textile fabrics formed of synthetic fibers.
In the process known as thermosol dyeing, a textile fabric formed of synthetic fibrous materials or blends of synthetic and natural fibers is printed or padded with a suitable preparation of dyestuffs, and the fabric is thereafter subjected to a thermosol heat treatment which fixes the dyestuffs on the synthetic fibers. The conventional method of thermosol heat treatment is carried out on a tenter frame wherein the fabric is gripped along opposite side edges by pins or clamps and transported through an oven where heated air is blown over the fabric. The time and temperature conditions to which the fabric is subjected are quite severe, with the temperature of the fabric approaching the softening point of the fibers. This results in harsh treatment to the fabric which is particularly troublesome with knit fabrics. Because of their delicate nature, knit fabrics are often distorted or stretched during the thermosol heat treatment.
It has been proposed in U.S. Pat. Nos. 3,567,356 and 3,837,796 to carry out the thermosol heat treatment with a drum dryer which directs air through the fabric rather than across the surface in order to hasten the fixation of the dyestuff and to thus reduce mistreatment of the fabric during the thermosol heat treatment. The particular dryer disclosed in the aforementioned patents utilizes a series of rotating perforated cylindrical drums and the fabric is transported along the surface of the rotating drums while heated air is directed through the fabric and through perforated drum and into the interior of the drum. While this drum type flow through dryer does tend to reduce mistreatment of the fabric during the thermosol heating treatment, it nevertheless has certain disadvantages or limitations. In particular, the flow through drum dryer disclosed in the aforementioned patents tends to distort the fabric and produce an undesirable ironed surface appearance since the fabric is held tightly against the surface of the drum by the flowing air. This holding of the fabric to the drum also restricts the ability to obtain longitudinal shrinkage of the fabric during the thermosol heating treatment.
With the foregoing in mind, it is a primary object of the present invention to eliminate the problems encountered with the thermosol heat treatment processes heretofore available. More specifically, it is an object of this invention to provide a method for the continuous thermosol dyeing of textile fabrics which reduces mistreatment and distortion of the fabric and which leaves the fabric with a desirable natural surface appearance.